A hydrogen storage tank that retains powdered hydrogen absorbing metal (hereinafter, referred to as MH) has been proposed. In the hydrogen storage tank, the MH absorbs hydrogen for storage, and the hydrogen is released from the MH when in use. However, in such a hydrogen storage tank, if the MH is retained in the tank without being held, the MH settles and may be partially compacted. If the MH absorbs hydrogen and expands in this state, an excessive stress is locally generated in the tank and cause adverse effect on the tank.
Thus, a hydrogen storage tank 6 as shown in FIG. 4 has been proposed. The tank 6 is formed by a tank main body 1, which includes a tubular body portion 2 and dome portions 3, which are respectively attached to the opposite ends of the body portion 2. The space in the body portion 2 is divided into retaining chambers 4 by partition members 5 located in the body portion 2. In the hydrogen storage tank 6, MH 7 is separately retained in the retaining chambers 4, and separately settles in the retaining chambers 4. This prevents partial compaction of the MH 7 in the body portion 2.
An MH container as disclosed in Patent Document 1 has also been proposed as one type of hydrogen storage tank that prevents partial compaction of the MH. A honeycomb structure that includes cells filled with the MH is inserted in the container, and shock absorbers are provided at the upper and lower ends of the honeycomb structure. An aerofin is wound around the outside of the container. In the container, the MH is prevented from moving to one side by the honeycomb structure and the shock absorbers.
Patent Document 2 further proposes a pressure container liner configured by a tubular first liner component and a pair of second liner components, which close the openings at the opposite ends of the first liner component. A reinforcement wall is provided in the second liner components.
When a hydrogen storage tank is used as a fuel tank for a hydrogen engine or a fuel-cell vehicle, the size of the tank needs to be reduced while maintaining the amount of hydrogen that can be supplied. To do so, it is required to increase the proportion of a hydrogen filled region (MH filled region) in the hydrogen storage tank. The proportion of the hydrogen filled region (MH filled region) means the proportion of the region that can be filled with hydrogen (MH) in the entire internal region of the hydrogen storage tank. In the hydrogen storage tank that includes the dome portions 3 provided on opposite ends of the tubular body portion 2 as shown in FIG. 4, the space S in the dome portions 3 may be filled with the MH to increase the proportion of the hydrogen filled region. In this case, however, the MH filling the space S in the dome portions 3 settles, and could be partially compacted at the bottom of the dome portions 3. If the MH expands in the compacted state, an excessive stress is locally generated.
Also, in the MH container disclosed in Patent Document 1, shock absorbers are provided at the upper and lower ends of the honeycomb structure to prevent the MH to move to the ends of the container. Thus, the ends of the container cannot be filled with the MH. Thus, the proportion of the MH filled region cannot be increased in such an MH container.
Furthermore, in the pressure container liner disclosed in Patent Document 2, the reinforcement wall provided in the second liner components is a member provided to increase the pressure capacity against the force that acts in the lengthwise direction of the pressure container liner. That is, the reinforcement wall is not provided in order to divide the space in the second liner components. Thus, in the pressure container liner, it is not taken into consideration that when the second liner components are filled with the MH, the MH in the second liner components may settle and become partially compacted.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2004-100926    Patent Document 2: Japanese Laid-Open Patent Publication No. 2005-61474